I accidently used Time Machine My Book disc must be erased? [

I just bought my external hard drive (My Book Essential).  I wanted to transfer my music from my PC to MAC it seems that i cant anymore cause I used Time Machine.  How can i fix this problem.  Can i reformat the external hard drive.  How can I restart the installation just like when you buy it new.

The easiest solution is to reformat the drive with a FAT32 file system.

Both Windows and OSX understand FAT32.